1. Field of the Invention
The present invention relates to a current detecting apparatus and more particularly it relates to a current detecting apparatus for detecting the flow of an electric current in the wire of a large current circuit.
2. Description of the Prior Art
Known current detecting apparatus of the above type which have heretofore been proposed include those having the following variety of constructions and these known apparatus have their own disadvantages as will be described hereunder.
(1) One form of such prior art apparatus is constructed so that all the current flowing in a wire is supplied to a coil or part of the current flow is supplied to the coil through a shunt, current transformer or the like to operate the contacts of a relay or the like with the magnetic flux generated by the coil (e.g., current relays). However, the apparatus of the type in which all the current flowing in a wire is supplied to the coil has the disadvantage of making the apparatus bulky in construction. Further, the apparatus of the other type employing a shunt or current transformer is disadvantageous in that the apparatus is expensive to manufacture and there are instances where an additional connecting operation is required. Further, with the latter type of apparatus employing a current transformer, the detection of DC current is impossible unless a specially designed DC current transformer is used.
(2) In other form of the known apparatus, the magnetic lines of force which are generated by the current flowing in a wire are passed to a Hall device and the detection of current is made according to the Hall voltage of the Hall device. While the apparatus of this construction has been put into practical applications as a DC current transformer, etc., the apparatus of this type has the disadvantage of high manufacturing cost since it requires a current regulating device for energizing the Hall device. Current detecting apparatus of the similar construction are also known in the art in which a magnetic induction device is employed in place of a Hall device. A disadvantage of this type of apparatus is that since current is detected in accordance with variation in the resistance of the magnetic induction device, it is necessary to use a transistorized detector and current regulating device thus making the apparatus expensive to manufacture and complicated in construction.
Therefore, there has existed a need for an improved apparatus of the above type which is capable of detecting the flow of current in a wire with a very simple construction. Specifically, there has existed a need for an improved current detecting apparatus of the portable type which is simple to operate and easy to attach on and remove from a wire without any need for connecting a shunt or the like to the wire.